The preparation, characterization and utilizaion of an antibody to the heavy chain of chicken gizzard myosin has ld to the demonstration of the presence of myoin in synaptic plasma membranes and synaptic junction fractions from rat brain. The two distinct bands observed in autoradiographs (MW 200.000 daltons) are now observed in post-synaptic density fractions. Investigations into the normal and lesion-induced distribution of glycocomponents in the rat hippocampal formation has utilized the coupling of lectins to horseradish peroxidase. A differential distribution of Con A recetors was observed; the inner third of the molecular layer of the dentate gyrus appears to contain the greatest quantity and the stratum lacunosoum-moleculare fails to react at Con A concentrations up to 250 g/ml. Following an entorhinal lesion (30 days post-surgical) however, Con A binding increased greatly in the entire molecular layer and stratum lacunosum-moleculare. This demonstrates a plasticity of glycocomponents during reactive synaptic growth in the mature brain. Implantation studies in the developing hippocampus reveal a pattern of afferent laminaton that implicates roles for temporal competition between homologous affeents and a hierarchical scheme of growth possibilities in developmental specificity. Using a histochemical stain technique for AChE, the pattern of initial outgrowth of fibers from a septal tissue graft was seen to terminate within the ra hosts' hippocampal formation 6, 8, 10, and 12 days following implant surgery. Separate studies observed this reaction when placed in either the occipital cortex or the entorhinal cortex; septal efferent patterns appeared to recreate that observed in normal animals.